Study reveals that Mann's Bristlecone pine trees may not be good "treemometers" after all

Dr. Michael Mann used tree ring core samples from Bristlecone pines in the Western United states as one of the most heavily weighted proxies used to make his infamous “hockey stick” Now it seems that even though temperature in these areas has been rising, the Bristlecones aren’t responding to it by increasing their range, and other tree species are jumping ahead in the same area.

Bristlecone pine trees in great basin are losing game of leapfrog with limber pine

From the UNIVERSITY OF CALIFORNIA – DAVIS

Gnarled, dead bristlecone pine trees, which can live to be more than 5,000 years old, stand where young limber pine grow around it. Limber pine is beginning to colonize areas of the Great Basin once dominated by bristlecones. CREDIT Brian Smithers/UC Davis

Bristlecone pine and limber pine trees in the Great Basin region are like two very gnarled, old men in a slow-motion race up the mountaintop, and climate change is the starting gun, according to a study from the University of California, Davis.

The study, published in the journal Global Change Biology, shows that the tree line has been steadily moving upslope over the past 50 years in the Great Basin. The region extends from California’s Sierra Nevada, across Nevada to Utah’s Uinta Mountains. Its north and south are framed by the Columbia and Colorado rivers’ watersheds.

The study also found that limber pine is successfully ? “leapfrogging” over bristlecone pine. They are growing in soils once almost completely dominated by bristlecone pine, and they are moving upslope at a faster rate than the bristlecone pine.

CHARGING UPSLOPE

“We are seeing very little regeneration anywhere in bristlecone ranges except in the tree line and, there, limber pine is taking all the good spots,” said the study’s corresponding author Brian Smithers, a Ph.D. candidate in the Department of Plant Sciences at UC Davis. “It’s jarring because limber pine is a species you normally see further downslope, not at tree line. So it’s very odd to see it charging upslope and not see bristlecone charging upslope ahead of limber pine, or at least with it.”

The study concludes that if bristlecone pine trees are unable to advance upslope because they are blocked by limber pine, bristlecones could face a reduction of their range and possibly local extinctions.

EARTH’S OLDEST LIVING TREES

Bristlecone pine trees are Earth’s oldest individual trees and can live for more than 5,000 years. No spring chicken, limber pine trees can live 2,000 years or more.

Both tree species have seen many climate changes during their time on Earth — from extremely warm periods to ice ages — and have slowly advanced across the landscape. Over millennia, bristlecone pine trees have moved from the lowlands of the Great Basin up to the current tree line. But, the study notes, neither bristlecone nor limber pine have ever experienced climate change and temperature increases as rapidly as what has been occurring in recent decades.

LEGACY EFFECTS

Smithers said he doesn’t expect bristlecone pine adult trees to be impacted much by current climatic shifts, as those trees are well-established. But how, if and where new bristlecone pine trees will regenerate is less certain, particularly as other species like limber pine take up valuable space for them to germinate.

“The things we’re doing today have legacy effects for thousands of years in the Great Basin,” Smithers said. “When those trees do start to die, they won’t likely be replaced because it’s just too hot and dry.”

The study suggests that land managers identify the specific bottlenecks for a species to live long enough to reproduce, and focus on that stage. For long-lived trees like bristlecone and limber pines, the bottleneck is at the time of their initial establishment, not hundreds and thousands of years into their adulthoods.

74 thoughts on “Study reveals that Mann's Bristlecone pine trees may not be good "treemometers" after all”

A rain gauge is a temperature proxy as good as a bristlecone pine tree ring. (Their growth is determined by the amount of water available in those few weeks between extreme winter cold and extreme summer heat.)

At a guess I would say that higher CO2 is helping them use water more efficiently, as happens in other plants.
Mann knew that tree rings were not a reliable proxy for temperature which is why he invented “Mike’s Nature trick” to “hide the decline” in Keith Briffa’s data point 1960 when it went totally the wrong direction against warming temperatures.
#MickeyMannKnew : sue him.

My thought exactly. Look at any given species of tree as you go higher up in altitude and it will have more and larger stomata as altitude increases in order to get enough CO2 for photosynthesis. At some point it has so many and such large stomata that the roots can no longer supply enough water to replace what is lost through transpiration. This is particularly true in thin soils that do not hold water well. Increase CO2 by 100 ppm and it is like moving the tree to a much lower altitude (would be like increasing O2 in the atmosphere would allow humans to live at higher altitude). The increased CO2 would allow the trees to be viable at higher altitude and the treeline would move up. The species moving fastest would be the ones producing the most viable seed and that are best suited for the local soil conditions. The rising of the tree line in this case would have nothing at all to do with temperature and would have to do with ability to get enough water to survive and CO2 increase causes the tree to lose less moisture at a given altitude by reducing the size and number of stomata.

The title of this post is misleading. From the linked abstract, the paper seems to have little to do with trees as temperature indicators. Instead, it’s mostly concerned with the ecological advantages limber pine juveniles have over bristlecone juveniles. Even that doesn’t say if the juveniles will eventually mature and out-compete the bristlecones. The paper does state that limber pines are rare at tree lines so maybe these observations just reflect from a short perspective rather than some fundamental change in physiology of the two species.

My takeaway:
“Earth’s oldest trees in climate-induced race up the tree line”
Since it has been argued that Bristlecone pines are an indicator of a changing climate, it seems they are not since they don’t seem to be responding to the warming over that area in the last century.

Bristlecones may not be treemometers, but they do indicate changing climates.
In bad times, they die back to just a strip of bark running up the side of the tree, thus the name “strip-bark,” then when the climate gets more favorable, they fill out and spread again. I believe that Ababneh identified bristlecones in her study as either full or strip-bark.
Here’s a strip-bark slice that shows how the strips expand when conditions get more favorable. Imagine trying to get a tree ring core sample from this tree.http://www.rockyhigh66.org/stuff/bristlecone1.jpg

I’ve no complaints about any critique of the study. It’s just that the term “Treemometer” has been used in reference to correlating growth rings and temperatures. This study is measuring treeline (upper elevation limit) changes and distributions of juvenile plants at treeline. The headline doesn’t really fit the story. Not a big deal.

Also, while I can’t confirm it without spending money to buy the study (paywalled) the photos appear to be of Bristlecone Pines in the White Mountains.
From a previous post:https://climateaudit.files.wordpress.com/2008/03/noamer47.gif
About this graph he (McIntyre) notes:
Here’s the MBH98 PC1 (bristlecones) again marking 1934. Given that bristlecone ring width are allegedly responding positively to temperature, it is notable that the notoriously hot 1934 is a down spike.
Since 1934 is generally accepted now to be the hottest year on record in 20th century it is indeed curious that 1934 in Mann’s data shows up as a down spike.
But seeing what happened with 1934, one has to wonder what do these trees really record in their tree ring growths? Is it temperature as Mann speculates? Or is it any number of other things related to plant growth in various combinations?
I was curious about what others had to say about these ancient pines. One of the first articles I came across was by NOVA, the PBS science program. They had an in-depth article on the “Methuselah grove” where the most ancient trees reside in the White Mountains of California’s Inyo National Forest.

The title of the post is what it is because this paper contradicts the notion that Mann’s favorite proxy is a good thermometer no matter what. It’s not. There are also two other linked articles BEFORE the paper is presented. Read those and maybe you’ll understand more about how the paper works into the topic.

It’s a verrrrrry well known fact that no tree is a treemometer, because growth is a composite.
It’s why when you think back to the botany you had, you aren’t grabbed by the realization that they can be.
That would be a great test question in any beginning botany class.
Yet all who have some botany under their belt, even helping one’s kids with homework, are baffled as to how such treemometer action could be asse rted as possible since growth is the function of many interrelated variables.
Mann’s work is and was grants and power scamming.

“Limber pine is successfully “leap-frogging” over bristlecone pine, probably because of its strong dispersal advantage and broader tolerances for establishment. This early-stage dominance indicates the potential for the species composition of treeline to change in response to climate change”

The magic “climate change” allegation. Alongs with nebulous waffle words; “probably”, “tolerances”, potential, etc.
At treeline the Limber Pine does not have an advantage over Bristlecone pines. Bird and animal seed dispersal is not a “climate change” effect.
Meanwhile, according to the National Forest Service; (I got the original link to the PDF from the NFS site.

“These findings suggest limber pine seed dispersal by Clark’s nutcrackers into more distant and open areas. Not only was clustering far less common for bristlecone pine seedlings, but it was not associated with increased dispersal distance or greater establishment in burn interiors (Table 3).
The 12% clustering we observed in bristlecone pine may suggest a minor role of animal-caching, but given the comparable dispersal distances and environments of clustered and solitary bristlecone pine seedlings, it appears unlikely that these clusters are arising from nutcracker caches. Instead, seeds may have been
transported short distances by seed-caching rodents, secondary to wind-dispersal (e.g., Vander Wall, 1992; Tomback et al., 2005).”

Clark’s Nutcracker is a mountain dwelling bird that collects pine seeds and cache’s them for winter. Apparently limber pine seeds are slightly preferred over bristle cone pine seeds.
Perhaps the study’s authors meant to use a different description “bird hop” rather than “leap frog”?

“Elevation: Across its range, Great Basin bristlecone pine occurs from 7,200 to 12,000 feet elevation [54,87]. Ranges by state are:
State Range
California 7,200-12,000 feet (2,200-3,700 m) [54]
Nevada 8,000-10,800 feet (2,400-3,300 m) [13,64]
Utah (7,200-10,700 feet (2,195-3,265 m) [136]Elevational range of Great Basin bristlecone pine has varied over time and space [79]. Hiebert and Hamrick [55] noted a downward shift in the current elevational range of 3 populations in southern Utah and eastern Nevada, with snags and cone-bearing trees, but no seedlings or saplings, above Great Basin bristlecone pine’s present elevational zone of establishment. LaMarche [71] noted a downward population shift on sites in the White Mountains. Great Basin bristlecone pine’s zone of establishment has been expanding downward in the White Mountains since around 1850. Great Basin bristlecone pine’s elevational range may also be shifting upwards in the White Mountains [134].
Climate: Great Basin bristlecone pine occurs in arid climates that are cold in winter and droughty in summer. Within Great Basin bristlecone pine’s geographic range, climate becomes increasingly dry from the Wasatch Range of eastern Utah to the White Mountains of western Nevada and eastern California. Growth of Great Basin bristlecone pine populations in eastern California and extreme western Nevada is affected by California’s mediterranean climate. More interior populations are influenced by the interior continental climate, which has summer monsoons. Correspondingly, eastern populations tend to be larger, denser, and have a greater range in their lower elevational limits [57].
The White Mountains lie directly behind the rain shadow of the Sierra Nevada, in the highest portion of the Sierra Nevada’s range. Summer rain is scarce; most precipitation falls as winter snow. Mean precipitation is 12 inches/year (300 mm/yr) [83], about 2.5 inches (64 mm) of which is rainfall during the growing season [78]. In July and August, mean monthly temperatures average 50 °F (10 °C). Mean monthly temperatures are below freezing from November through April. In contrast, mean annual precipitation on Great Basin bristlecone pine sites in the Snake Range of eastern Nevada is about twice that of Great Basin bristlecone pine sites in the White Mountains (Pace and others 1968, as cited in [78]). The ability of Great Basin bristlecone pines to grow to full stature up to treeline in the White Mountains, while forming krummholz at treeline in eastern Nevada, is probably due to differences in climate. Physiological and morphological adjustments made in the needles in response to summer drought in the White Mountains also protect trees from winter desiccation, which is largely responsible for inducing krummholz growth [78].”

Both pines are long lived species. Plenty of time to spread seed into suitable habitat.
The alleged research abstract reads like another study conducted from solid confirmation bias positions.

Forgive me for not being able to supply links, but as I recall there are dead bristlecone pine stumps at higher elevations, that grew and died during warmer times. Originally they were used to affirm the reality of the MWP, but then such evidence became “unfashionable”.
If the pines could survive that yo-yoing of the treeline, they’ll do OK now.
I also recall various excuses being made about how it was “too expensive” to go to high altitudes and double check certain things about the bristlecone pines, back in the day. So what did Steve McIntyre do? He drove up there while on vacation, God bless his soul! It was one of the funniest posts at Climate Audit, and made certain “climate experts” look like complete weenies who don’t dare step outside.
Those were the days!

“Caleb September 15, 2017 at 7:38 am
…
If the pines could survive that yo-yoing of the treeline, they’ll do OK now.
I also recall various excuses being made about how it was “too expensive” to go to high altitudes and double check certain things about the bristlecone pines, back in the day. So what did Steve McIntyre do? He drove up there while on vacation, God bless his soul! It was one of the funniest posts at Climate Audit, and made certain “climate experts” look like complete weenies who don’t dare step outside.
Those were the days!”

Agreed!
I like your description of the weenies, which they are.
I don’t remember McIntyre’s article as being all that funny, except in parts. Weenies should realize that many folks with a healthy dose of common sense aren’t put off by weenie posturing, whining and tantrums.
The weenies want ladies to faint and men to cheer from weenie tales of derring-do, dangers and horrendous conditions weenies face.
Typical self centered weenie fantasies.
Far too many realists understand that journeys start by putting one foot in front of another; no matter how distant or difficult the goal.
Weenies prefer fine foods, luxurious accommodations and lots of workers to do the dirty work.

Well, the usual (holding down the fort till Jim Steele gets here):
1) How long have those bristlecones in the picture been dead?
2) What killed them?
3) Did they die in the last 30 years, when this 1 degree increase is supposed to have occurred?
4) Does not a one degree T change correspond to about 200 vertical feet?
5) Did the limber really march up the hill steadily, in spite of the “pause”?
6) Have native insects and invasive fungus had nothing to do with it?
7) Aren’t 30 years too short a span to deduce much about trees that live thousands of years?
8) Could not the relation between the two species be analogous to that between quaking aspen and pine? (aspen are opportunistic but slowly give way to conifers)
9) Who is responsible for widespread dissemination of this report?
–AGF

But, the study notes, neither bristlecone nor limber pine have ever experienced climate change and temperature increases as rapidly as what has been occurring in recent decades.
Credibility of this study just flew out the window.

As a non-scientist it seems like water supply and NOT a degree or two in temperature (considering most trees experience a wide range of temperatures seasonally) would have a lot more to do with tree growth each year. How can tree rings ever be used as a proxy for temperature??? It doesn’t seem logical.

Perhaps. We planted some Colorado Bristlecones in southern Wisconsin 40 years ago and they are doing just fine. Bristlecone will always do better at high altitude than other pines as they have a wax coating on their needles that protects them from harsh UV and dry winds. Eventually they’ll power up and over the Limber pines.

It’s a bit amusing when they try to infer we are warming unusually with trees ‘leapfrogging’ beyond what was previously the highest growing. Here in Colorado, when tromping about near treeline, the limit of current growth, there always seems to be some ancient, disintegrating stump a few hundred feet higher in altitude, from when it actually was warmer.

“Here in Colorado, when tromping about near treeline, the limit of current growth, there always seems to be some ancient, disintegrating stump a few hundred feet higher in altitude, from when it actually was warmer.”
But that is not a peer reviewable temperature proxy – so it doesnt count
Same as those tree stumps uncovered by the retreating ice glaciers.
(sarc)

How bout we just grab a bunch of seeds for both and spread them everywhere. Do that with all sorts of plants and trees. With the increase in CO2 and the wet years we’re in now most should thrive. That’ll screw with everybody and maybe we can be done with all these stupid studies that have no meaning.

If nothing else, the previous articles about the Bristlecone indicate that Mann was at least as incompent as anything more nefarious as a researcher. SImple, elementary science would have expected any proxy for temps as antilogical as tree rings (which 99% would probably assume indicates water prevalence) would have at least been checked against other proxies or, especially, against more recent and reliable temp readings. Then, of course, there is the other problem of assuming the climate of that small area of the planet is a good proxy for the planet as a whole.
Didn’t Mann actually argue that the Little Ice Age was confined to America and parts of Europe?
Which, of course, we now know better.

If the researchers do not fully understand all the biology, growth strategies, etc, of both species how can they conclude this has anything to do with local climate change much less global climate change? Competition between species is something else environmentalists seemed to ignore. Competition between species is often warfare. I remember sitting in on the first high speed video of a coral reef where corals were attacking each other. Interesting but no surprise to me but it was shocking to many of the young scientists in the auditorium. A couple turned away; they couldn’t watch.

Edwin, you say, ” Competition between species is something else environmentalists seemed to ignore. Competition between species is often warfare.”
Does this remind anyone of the spotted owl which was used by the eco-nuts to nearly kill the timber industry in the Pacific Northwest? The reality was that the barbed owl was out competing the spotted owl and that its problems had little or nothing to do with logging.
Data remains of little use in religious wars.

Just being persnickety, but high speed video of coral will be really boring. I think what you meant to say was time-lapse images of coral. Time-lapse video “compresses” the temporal frame an appears to speed things up. High speed video “stretches” the temporal frame and makes things appear to move slower.

Available soil moisture at the roots is what makes trees grow bark. So thicker tree rings are a better simple proxy of rainfall than temperature, but the rains have to be of sufficient duration that it soaks into the ground as well. So it is quite possible that a longer cooler rainy spell will cause more bark growth than an average higher temperature.

Bristlecones are amazing, they can and do grow in much more favorable places, like lower elevations or in your yard. Then they grow like a more average tree and die much younger. The extreme conditions (poor soil and nasty weather) where we find ~6,000 yr old Bristlecones are the reason they live so long.

My objections I stated TEN years ago at Climate Audit,was that Bristlecone Pine tree ring data are not a valid measure of “global” temperature,as it inhabits in some of the harshest regions of America. It grows in a tiny area of the United States,in short growing season,in places that are out of step temperature wise in the region.
It is NOT a credibly representative sample of the continent,when it inhabits so tiny an area of it. The database size is laughably small!
That was when I knew the paper was pure junk.

Bristlecones record alpine climate strong affected by snow accumulation and date of snow melt, not continental climate. Snow melt is controlled by slope orientation and angle of inclination among other factors having nothing to do with climate. The older bristlecones are south slope facing on hot rock, the younger bristlecones on north facing slopes have much wider rings and are more susceptible to fungal infection. Your tree results depends on the population of bristlecones you select. There is no such thing as a universal bristlecone tree ring response for a site. Two trees next to each other will have different tree ring widths so they cannot be read as accurate climate surrogates. The way Mann got around this was to take one pine ring sequence, to get rid of the variability a population of rings would show.

Many tree ring records of bristlecones are from dead trees. I would presume the record of dead, desiccated trees is different that sampling from living trees. Some ring records come from branches found lying on the ground. I recall the oldest ring record is from a dead branch found on the ground unattached to any tree.

“…Hey now, next you’re going to say one temperature measurement per 25,000 square miles is sufficient…”
This is exactly what Ms Marohassy found in Australia. Interpolation between stations spaced hundreds of miles apart was quite acceptable to the Weather Office.
This is also happening in the States, as Anthony discovered during his epic study…

The limber pine is a timberline species in it’s southern range. That is the Sierra Nevada and southern California ranges. It also is better at distributing itself. A bigger seed more appealing to Clark’s nutcrackers, the bird responsible for it’s distribution. So climate change probably is less responsible than meets the eye

Maybe one of the trees has reproduction primarily vegetative – by layering, rather than pollen/seeds.
Also, …
Steve McIntyre’s “Ohio State Paper” debunked the Bristlecone pine’s usage by Mann and others.
I think that was in early 2008 (?).
Whatever is now going on will be nice to know. Full paper would be nice.

Average temps reported by the weather station at Ely Air Field / Yelland Field do not show a warming trend – when looking back to its establishment in the early 1970s.
While we might attribute a supposed global temp rise in recent several decades to various observations, does it not make sense that the overall warming trend would have to also be obvious in the local area of interest?
Although these trees have experienced no warming in the recent 50+ years, do they somehow know that there is a global effect to which they should respond?
[Go to “Wolfram Alpha,” and enter “average temperature last 80 years Great Basin.”]

“Bryson and others [24] found that Great Basin bristlecone pines in the Schulman Grove of the White Mountains occurred in pure stands on north-facing slopes. South-facing slopes were occupied mostly by limber pines, with few or no Great Basin bristlecone pines.”https://www.fs.fed.us/database/feis/plants/tree/pinlon/all.html

When constructing a time series of proxies for anything, if you weight the proxies which follow a pattern you are looking for far more heavily than those that don’t, my guess is that you will probably find it.

But, the study notes, neither bristlecone nor limber pine have ever experienced climate change and temperature increases as rapidly as what has been occurring in recent decades.

And how do they know that? Have they been able to refine the data to get changes occurring in less than 3 decades? My understanding is that they can only determine rates over a century – and the average has been around 1K per century. What was the rise over the 20th century? Oh… about 0.9K. And the rise in the recent decades? Well, for the past two decades, there has effectively been no rise at all; over the past 5 decades, there has been a rise of about 0.6K – extrapolate that, and you get… ooh, look!… a rise of just over 1K per century. Hardly Earth-shattering or tree shaking, I would have thought. I wonder what “the studies” will note when this “meteoric” rise of not very much at all turns into an undeniable plummet?

Tree rings record nothing accurately. They are impacted by dozens of things including pest infestation, soil fertility, soil depth, soil composition, soil moisture, slope angle, slope orientation, snow depth and duration, competition for sunlight, rainfall, freeze days, winter snow and glaze damage, freeze season start/end, temperature, tree age, wind speed and duration leading to desiccation, soil creep, animal grazing, fungi and lichen growth, and rainfall season (dates and times and spread of rain over a season), etc. To claim you can see one of them over the others is absurd. In fact, rainfall and wind are yin and yang counter components making it impossible to gauge to rainfall vs the moisture a tree gets.

Love L&H
It’s interesting how movies capture history. I know two things were present in the 1930s. Credit cards (His Girl Friday) and general knowledge of reincarnation (L&H’s Flying Dueces).
Hardy: What would you like to be when you come back?
Laurel: Myself. I really like who I am.
Hardy: You can’t come back as yourself!

Don’t always produce annual rings means sometimes they do. Dead bristlecones don’t produce anything. Nobody said this stuff is going to be easy. If nothing else they can be examined as ice cores are examined for tell-tale chemical compounds that vary over the life of the tree. A cross section of a 6,000yo tree is a trip back in time even as it incorporated older individual growths into the expanding mass of the present trunk.

This one used a cunning ploy to become the worlds oldest tree. It’s interesting that longevity and a harsh environment go together.
The world’s oldest recorded tree is a 9,550 year old spruce in the Dalarna province of Sweden. The spruce tree has shown to be a tenacious survivor that has endured by growing between erect trees and smaller bushes in pace with the dramatic climate changes over time.https://www.sciencedaily.com/releases/2008/04/080416104320.htm

The coming study may contain …
For hundreds of year these two old Bristlecones were kept alive by the symbiotic relationships by which the trees would provided shelter and food for many squirrels and rodents, this in turn attracted great packs of prairie dogs that would periodically visit to feast on the wildlife and mark the territory in great volumes.
This symbiosis lasted until man arrived and killed off most of the dogs, rodent population, and all the squirrels. When that happened the Bristlecones were only left with a pot to pi$$ in.

There are mature Limber and Bristlecone “sky islands” all over the Great Basin and down into the Mojave and Angeles mountains. Usually on the NE facing slopes and cols. Usually with few if any juvenile trees.

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